ci: add helper script to test updated repository metadata

[kenhys]

Use case:

• upload pre-built packages on test/experimental before release
• check whether repository metadata is correctly updated

Currently added helper script will be executed on local machine.

If repository metadata is valid, it reports something like:

Complete!
Succeeded to install 5.0.3 on "amzn" from exp/lts/5

OK: debian:bullseye exp/5
OK: debian:bullseye exp/lts/5
OK: debian:bookworm exp/5
OK: debian:bookworm exp/lts/5
OK: ubuntu:focal exp/5
OK: ubuntu:focal exp/lts/5
OK: ubuntu:jammy exp/5
OK: ubuntu:jammy exp/lts/5
OK: centos:7 exp/5
OK: centos:7 exp/lts/5
OK: almalinux:8 exp/5
OK: almalinux:8 exp/lts/5
OK: rockylinux:9 exp/5
OK: rockylinux:9 exp/lts/5
OK: amazonlinux:2 exp/5
OK: amazonlinux:2 exp/lts/5
OK: amazonlinux:2023 exp/5
OK: amazonlinux:2023 exp/lts/5

[kenhys]

still work in progress. not ready yet.

[kenhys]

If there is something weird, it reports:

...
OK: ubuntu:focal exp/5
NG: amazonlinux:2023 exp/5
OK: amazonlinux:2 exp/5